While the uploading of photos to social media networks to share them with their family or friends has dramatically increased, there is also much concern about personal privacy which may be leaked through the uploaded photos.
In efforts to protect the personal privacy, some social media networks allow users to add group/tag or assign permission as to who can access uploaded photos. Also, users can blur a part of human faces in photos before uploading to avoid a risk that strangers see his/her own family or friends. However, most of the solutions are focused on pre-image processing before uploading images or blocking unauthorized users from downloading or capturing the images, but do not address post-image processing issues after uploading or downloading the images.